1. Field of the Invention
The present invention relates to an apparatus and method for forming 2D views of a structure and, more particularly, to an apparatus and method for forming 2D views of a structure from 3D point data.
2. Description of the Related Art
It is often desirable to have computer models that represent the as-built configuration of large physical structures, such as a petroleum refinery. The computer models are constructed by acquiring geometric information about the to-be-modeled structure. One technique for acquiring the geometric information is to use a laser scanning system. In a laser scanning system, the to-be-modeled structure is scanned with a laser from a plurality of views.
Each scan includes a plurality of scan points that cover a view of the structure. Each scan point has a measured location in 3D space (3D point data), usually in terms of an (x,y,z) point in the scanner""s local coordinate system, or a transformed coordinate system. In some cases, the 3D point data also includes data that indicates the intensity of the laser light reflected from the point.
When a view is scanned, the laser scanning system generates 3D point data for a large number of points. The collection of scan points from one or more scans is often called a scan cloud. The scan cloud typically has points that lie on many different surfaces, depending on the view that was scanned. For example, a scan taken at a petroleum refinery may include a point cloud that has points on pipes, elbows, valves, pumps, and structural steel members.
Once each view of the structure has been scanned, a triangulated mesh that joins the 3D point data can be formed using any number of well-known techniques. When the mesh is rendered on a computer display it provides more feedback to the user about the surfaces in the view than when the points alone are viewed. The mesh looks more like the real surfaces that were scanned, and foreground meshes occlude distant meshes. It should be noted that foreground points do not occlude. background points, so points are always in view. Therefore, triangulated meshes are very useful for visualization purposes.
If geometric data is needed rather than simple visualization, the 3D point data can be processed to form a 3D model of the structure. In addition to the 3D model of the structure, it is often desirable in architecture, engineering, and construction applications to create 2D views of the 3D point data in particular projections, such as plan views or elevation views. The 2D views are relatively straightforward to create from a 3D model of the structure, but are extremely difficult to create from the 3D point data that are used to form the 3D model of the structure.
If the time required to create a model of a structure is divided between a first data gathering step, where the structure is physically scanned to produce the 3D point data, and a second data processing step, where the 3D point data is processed to form the model, the data processing step would require significantly more time. As a result, the data processing step is a significantly more expensive step to complete than the data gathering step.
Thus, due to the high cost of the data processing step, and the difficulty associated with utilizing the 3D point data directly, it is often cost prohibitive to laser scan a structure for the sole purpose of generating 2D views of the structure. Thus, there is a need for an apparatus and method that easily form 2D views of a structure from the 3D point data.
The present invention provides an apparatus and method that form 2D views of a 3D structure. The apparatus of the present invention includes means for forming a number of intersection polylines. The intersection polylines have groups of polyline points such that each intersection polyline has a group of polyline points. The apparatus also includes means for forming a sequence of features from each group of polyline points. The apparatus further includes means for joining consecutive features in each group of polyline points to form a 2D view.
The method of the present invention includes the step of forming a number of intersection polylines. As above, the intersection polylines have groups of polyline points such that each intersection polyline has a group of polyline points. The method also includes the step of forming a sequence of features from each group of polyline points. The method further includes the step of joining consecutive features in each group of polyline points to form a 2D view.
A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description and accompanying drawings that set forth an illustrative embodiment in which the principles of the invention are utilized.